Laws of Land Warfare
The Laws of Land Warfare are both a term, in customary international law especially preceding the Geneva Conventions, and also a United States Army manual for the rules to be followed in war.  Article 4 of the Third Geneva Convention uses the phrase "laws and customs of war" as those that must be followed by soldiers in the field. They are rules for the conduct of warfare, the jus in bello aspect of just war theory.
The first U.S. field legal regulations were the Lieber Code of 1863.  FM 27-10, supplemented by local commanders' rules of engagement and other directives, remain in effect. The Laws complement the Uniform Code of Military Justice, which includes conduct off the battlefield.
- Field Manual (FM) 27-10: Laws of Land Warfare, United States Army
- Instructions for the Government of Armies of the United States in the Field (Lieber Code), International Commission of the Red Cross, 24 April 1863